U.S. Pat. No. 7,104,695 B2 discloses an asymmetrical hub bearing assembly, comprising a hub with a flange extending radially outwardly from an axial end for mounting the wheel of a vehicle, an outer ring with axially spaced raceways, and a plurality of rolling elements arranged in two rows in the annular space between the outer ring and the hub. The pitch circle diameter of the row of rolling elements arranged at the axially outer side (outboard), adjacent to said flange, is greater than the diameter of the pitch circle of the rolling elements of the row on the axially inner side (inboard). Due to this arrangement, the distance between the pressure centers where the contact angle of the two bearing rows intercept the hub axis can be increased; this provides a higher camber stiffness. The outboard row intercepts the hub axis outboard of the hub flange, which balances the loads on the system more evenly between the inner and outer bearing rows. As an effect of the asymmetric arrangement, the outboard row can accommodate more rolling elements, and thus increase the load capacity of the bearing, at equal size of a symmetric unit. The asymmetric design allows to place the pressure center farther outboards than a symmetric unit, without having to increase the contact angle and without reducing the bearing capacity of the bearing in a radial direction. The asymmetrical arrangement, finally, increases the load bearing capacity without requiring modifications to the suspension strut of the vehicle.
The radial flange of the hub provides a number of holes to allow mounting of the vehicle wheel by means of bolts. The flange also has a flat radial surface, at the axially outer side, which defines a precise reference surface against which the brake disc and the wheel may rest. The hub also forms a centering annular projection which extends in the axially direction beyond the radial flange. This projection is designed to enable a preliminary support and centering of the wheel, before it is fixed, in a perfectly centered position, via the fastening bolts that are inserted through the holes of the flange.
With sports cars, a need is felt to have a single central threaded fastener to quicken the assembly and disassembly of the wheel. It is an object of the invention to provide an integrated hub-bearing unit assembly being compact, lightweight, allowing the wheel to be quickly mounted or removed that meets the needs of the industry.